The present invention relates to the manufacture of melt spun polymeric filaments and, in particular, to the quenching of spun filaments emerging from the spinneret.
The manufacture of melt spun polymeric filaments is typically achieved by extruding a molten polymer, such as polyester, polyamide, etc., through a spinneret and then cooling the filaments thus formed. Therebelow, the filaments are converged and gathered at a guide and delivered to a bobbin or further treatment station.
The manner in which the filaments are cooled has a significant impact on the resulting quality of the filaments. A typical cooling technique involves a gas quench in which cool air is blown across the filaments as they emerge from the spinneret. In instances where the filaments are extruded in the form of a circular array, it is common to utilize an outflow quench technique in which the filaments are passed downwardly in surrounding relation to an upwardly extending air pipe, the latter being arranged generally coincident with the central axis of the group of filaments. Quench air is directed radially or laterally outwardly through the filament group from an upper, apertured end of the pipe, the air preferably dispersed by a porous sheathing surrounding the apertures. There is thus produced a controlled cooling of the filaments. For example, see U.S. Pat. Nos. 3,135,811; 3,259,681; 3,858,386; and 3,969,462. There has also been prior public use for more than one year of the apparatus shown in FIGS. 1A and 1B.
In FIGS. 1A, 1B there is depicted a conventional melt-spinning apparatus 10 wherein a conventional filter pack 12 carries a conventional spinneret 14 through which is downwardly extruded a molten polymer such as polyester or polyamide for example, to form filaments. The spinneret is of a conventional type comprising holes arranged in an annular pattern so that a group 15 of circularly arranged filaments 16 is formed. The holes of the spinneret are preferably arranged in a series of circular rows having a common central axis. The spun filaments are split into two groups and travel downwardly to two turning guides 9, or godets or rolls, at which they are gathered and redirected, in conventional fashion.
The pack 12 is mounted on a conventional superstructure 20, and the filaments travel downwardly within a cabinet 22 closed at least on three sides and possibly open at the fourth side for operator monitoring purposes.
Quench gas in the form of air is provided to cool the filaments 15 emerging from the spinneret. The quench gas is delivered through an upwardly extending quench gas conduit 1 which includes a gas supply portion 2 and a gas discharge portion 3, which comprises a perforated hole pattern to obtain a required profile. The gas supply portion extends horizontally into the group of filaments and forms an elbow 4. Openings are provided in the gas discharge portion to discharge quench air radially outwardly, with the desired profile, through the surrounding filaments. A porous sheath 5 surrounds the gas discharge portion to uniformly disperse the discharging air.
The upper end of the conduit 1 includes a pin 6 which is received in an opening of the spinneret 14 to prevent lateral displacement of the conduit 1.
As is apparent from FIG. 1B, the filaments 16 are separated into two bunches 7, 8 to avoid contacting the elbow portion of the conduit 1. The separate filament bunches are gathered and redirected at a pair of turning guides 9.
In operation, quench air is delivered via the conduit 1 and is discharged radially outwardly from within the group of filaments emerging from the spinneret. The quenched filaments are separated into bunches 7, 8 and are gathered and redirected at the guides 9 for collection, or further treatment.
It will be appreciated that the conduit 1 is often of substantial height, thereby increasing the overall height of the machine and rendering it difficult to maintain the conduit in alignment with the longitudinal axis defined by the filament group. This arrangement also renders it difficult to maintain constant the distance from the spinneret to the uppermost quench air stream. Air gaps 16A are formed between the filament bunches 7, 8 which gaps promote undesirable air turbulence. To limit the ability of the filaments to contact the elbow, the diameter of the conduit 1 is minimized, but this restricts the quantity of air flow that can be conducted and also increases the pressure drop.
As previously indicated, the lower portion of the air pipe forms an elbow and passes horizontally through the group of filaments above the turning guide. In order to prevent the downwardly converging group of filaments from rubbing against the elbow, the pipe diameter is minimized and the filament group is divided into two bundles, each bundle fed to a separate turning guide, as depicted herein in FIG. 1B, for example.
The minimization of the air pipe diameter at low pressures below 5 psi results in the quantity of air flow being less than that normally desired for optimum cooling performance. In addition, enlarged air gaps are formed between the separated bundles, which gaps promote air turbulence, non-uniform quenching of the filaments, and increased drag action on the filaments. Also, the extra handling of the filaments increases the overall wear and tear to which they are subjected.
As regards the air pipe itself, the elbow must be placed at a level sufficiently below the quench zone to allow the filaments to be effectively divided into separate bundles. This results in a relatively long air pipe height which increases the overall machine height and renders it difficult to maintain the pipe aligned with the central axis of the filament group to assure that uniform quenching action is achieved.
It will be understood that the vertical distance between the extrusion holes of the spinneret and the uppermost stream of cooling air is of critical importance regarding the quality of filaments being produced. It is thus required that a predetermined distance be maintained at all times, a feat not easily accomplished with an air pipe of relatively great height which is anchored somewhere at its lower end remote from the spinneret.
It will also be appreciated that the splitting of the filament group into bundles considerably limits the available free area around the filament travel path and thus restricts the operator's access.
It is, therefore, an object of the present invention to minimize or obviate problems of the type discussed above.
Another object of the invention is to provide a filament quench which does not require the passage of a conduit laterally into the filament group.
It is an additional object of the invention to provide a filament quench which quenches all filaments equally and minimizes the action of air drag and air turbulence on the filaments.
A further object of the invention is to provide a filament quench which maximizes the quantity of quench gas flow attainable.
Another object of the invention is to provide a filament quench which prevents unlubricated filaments from being dragged across a surface, and therefore minimizes wear and tear on the filaments.